ANONYMOUS Garage Band's sounds are great, but the parameter arrays for the synth modules are rather basic, and adjustments on the fly can't be automated. The lack of MIDI output is the biggest hinderance to any musician with existing MIDI equipment; this is the "missing link", as it were, without the expense of the oxymoronically named Logic.
(Oh, now I understand: its called "Logic Audio" because (a) it uses 1s and 0s, not because the user interface is sensible or intuitive; and (b) "Obtuse, Time Wasting Clap-Trap Audio" didn't appeal to the marketing depertment, even with "Platinum" tacked on the end)
(Version 1.14)